Conventionally, an air-conditioning vapor-compression refrigeration cycle device, which is applied to an air conditioner, is known to include an internal heat exchanger. This kind of internal heat exchanger is designed to exchange heat between high-pressure and low-pressure side refrigerants in a cycle, thereby exhibiting the effect of enlarging a difference in enthalpy (refrigeration capacity) between outlet and inlet-side refrigerants in another heat exchanger serving as an evaporator to improve a coefficient of performance (COP) of the cycle.
For example, Patent Document 1 discloses an air-conditioning refrigeration cycle device including an internal heat exchanger. The refrigeration cycle device is configured to be switchable between a refrigerant circuit for an air-cooling mode of cooling ventilation air to be blown into a space to be air-conditioned and a refrigerant circuit for a dehumidification heating mode of reheating the ventilation air cooled and dehumidified.
More specifically, the refrigeration cycle device described in Patent Document 1 is configured to switch to the refrigerant circuit in the air-cooling mode. In the refrigerant circuit, a refrigerant circulates through a compressor, an exterior heat exchanger, a high-pressure side refrigerant passage of the internal heat exchanger, a decompression device for an interior evaporator, the interior evaporator, a low-pressure side refrigerant passage of the internal heat exchanger, and the compressor in this order. The exterior heat exchanger exchanges heat between the refrigerant and outside air. The interior evaporator exchanges heat between the refrigerant and the ventilation air to be blown into the space to be air-conditioned, thereby cooling the ventilation air.
The refrigeration cycle device is configured to switch to the refrigerant circuit in the dehumidification heating mode. In the refrigerant circuit, the refrigerant circulates through the compressor, an interior radiator, a branch portion, the high-pressure side refrigerant passage of the internal heat exchanger, the decompression device for the interior evaporator, the interior evaporator, a merging portion, the low-pressure side refrigerant passage of the internal heat exchanger, and the compressor in this order. At the same time, in the refrigerant circuit, the refrigerant also circulates through the branch portion, a decompression device for the exterior heat exchanger, the exterior heat exchanger, and the merging portion in this order. The interior radiator exchanges heat between the refrigerant and ventilation air cooled by the evaporator to thereby heat the ventilation air.
Thus, the refrigeration cycle device described in Patent Document 1 is designed to enhance the refrigeration capacity of the interior evaporator in both operation modes of the air-cooling mode and dehumidification heating mode, thereby improving the COP of the cycle.